Download Vertebral Heart Scale

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Vertebral
Heart Scale
Amara Estrada, DVM, DACVIM (Cardiology)
Stacey Fox-Alvarez, DVM, MPH
University of Florida
1
d Illustration of VHS
YOU HAVE ASKED...
How do I calculate a vertebral
heart scale (VHS)?
THE EXPERTS SAY...
The vertebral heart scale system (ie,
vertebral heart size) was developed as
a means to objectively evaluate cardiac
size among dogs of different breeds and
thoracic conformations.
VHS = vertebral heart scale
WHAT YOU WILL NEED
hT
o calculate a VHS, a lateral thoracic
radiograph in right or left lateral
recumbency is needed. If using plain films,
calipers or a ruler will be necessary to hold
the measurements. If using digital films,
calipers or electronic calipers can be used.
hT
he best possible technique and
positioning of the patient should be used to
prevent rotation from affecting
measurements and to make serial imaging
comparisons more reliable.
calculation in a normal
dog. On a lateral
radiograph, a line is drawn
from the carina to the
most ventral aspect of the
heart. This line is the “L”
or long axis line. A line is
drawn perpendicular to
the long axis at the widest
portion of the heart,
extending to the cranial
and caudal borders. This
is the short axis or “S”
line. These lines are
transposed using calipers
extending along the spine
from the cranial aspect of
T4. The number of
vertebrae traversed
(rounded up to the
nearest tenth) are added
together for the VHS.
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ses of Vertebral Heart Scale
U
The VHS was established to create a
more objective way of diagnosing cardiomegaly via thoracic radiography.
Individual dogs can have values that fall
outside of the normal range without cardiac disease, so it should not be used as
the only means of diagnosing cardiac
disease in any given patient.
Author Insight
Right or left lateral
recumbency is
acceptable.
If taking serial
images, they should
be done using the
same side.
h The long axis
should be drawn
from the level of the
carina. The short
axis should be
perpendicular to
the long axis.
h
CHF = congestive heart failure
DCM = dilated cardiomyopathy
DV = dorsoventral
MVD = mitral valve disease
VD = ventrodorsal
VHS = vertebral heart scale
In addition to a thorough history and
physical examination, VHS can be used
to raise clinical suspicion of heart disease. VHS is useful for monitoring a
patient in which heart disease is suspected (Figure 1, previous page), or in
tracking changes in progressive cardiac
disease over time.
VHS has been shown to correlate with
other means of measuring cardiomegaly
(ie, ECG, echocardiography) in dogs
with progressively increasing heart size,
and it is considered by some to be the
gold standard in determining cardiomegaly in dogs.1 The authors believe
many dogs with presumptive MVD can
be managed effectively by use of a thorough physical examination and basic
diagnostics, such as a VHS and measurement of blood pressure. As guidelines
for the treatment of heart disease in veterinary medicine evolve, it will become
increasingly important to accurately
stage patients with these conditions to
determine when medical treatment is
indicated. VHS calculation can be an
important component to the staging of
cardiac disease.
Pimobendan and ACE inhibitor treatment for Doberman pinschers with preclinical dilated cardiomyopathy (DCM)
have both been shown to delay onset of
clinical signs2,3 such as sudden death or
congestive heart failure (CHF) and
50 cliniciansbrief.com April 2016
should be considered when imaging
yields evidence of preclinical disease (ie,
left ventricular enlargement, decreased
contractility identified on echocardiography). Results are mixed when evaluating the use of ACE inhibitors in
preclinical dogs with stage B2 MVD.4,5
ACE inhibitors are currently recommended for these patients by some specialists, as well as the majority of the
members of the ACVIM consensus panel
for MVD.6 As more studies evaluate the
use of medical intervention to delay the
onset of CHF in dogs with preclinical
cardiac disease, treatment recommendations will continue to change.
Serial measurements and rate of change
of VHS have been demonstrated to be
predictive of the onset of congestive
heart failure in Cavalier King Charles
spaniels with mitral valve regurgitation.7,8 Several studies in this breed have
shown that the rate of change of VHS on
serial radiography (ie, every 6-12
months) remains steady up until 6-12
months prior to onset of CHF, when it
increases at a much faster rate.7,8
The ACVIM consensus statement on
degenerative MVD recommends baseline thoracic radiography for dogs with a
new murmur, then annually thereafter.6
For practitioners adhering to these
guidelines, annual calculation of VHS
and rate of change from previous imaging should become standard practice
and may help identify those patients at
higher risk of developing CHF in the
coming year. Figure 2, page 52, illustrates annual radiographs taken in a
patient with progressive cardiomegaly.
The VHS has been shown to be useful
when determining whether a cough is
cardiogenic, pulmonary, or mixed in origin for dogs with MVD.9 One study found
that a VHS >12.0 was suggestive for a cardiac component to cough in dogs with
MVD.9 It is important to note that among
these dogs, some were determined to
have a cough of mixed cardiac and pulmonary origin.
VHS has also been shown to be useful
when diagnosing CHF as a cause of dyspnea in cats, which is notoriously difficult because of the varied appearance of
pulmonary edema in this species. One
study found that a VHS >9.3 was highly
sensitive for CHF as a cause of dyspnea
and that cats with a VHS <8.0 were
unlikely to have dyspnea secondary to
cardiac disease.10 Unfortunately, the
presence of pleural effusion, which is
common in cats with heart failure, can
obscure the cardiac apex. This makes the
VHS calculation difficult or impossible to
accurately determine in some animals.10
studied individually fall within the
normal range. However, several
breeds have normal VHS values that
would suggest cardiomegaly using
the original scale.
Of the breeds evaluated to date, the
boxer, bulldog (French and
English), Boston terrier, Cavalier
King Charles spaniel, Labrador
retriever, pug, Pomeranian, and
whippet have been found to have
average values that are much
higher than other dog breeds. New
sets of normal values have been
developed for use in these
breeds12-14 (Table 1).
A normal range of 6.7-8.1 has been
established for cats.15
Normal Values
The short and long axis measurements
can also be taken on ventrodorsal (VD)
or dorsoventral (DV) projections, but
this measurement is not as consistent
between animals. Measurement from a
lateral projection is recommended, if
possible. The reference values for vertebral heart scale measured on VD and DV
radiographs are 9.4-11.0 and 8.8-11.7,
respectively, for dogs.11
The published range for a normal VHS is
9.2-10.3 on a lateral radiograph, with
10.5 suggested as the cutoff for clinical
determination of cardiomegaly in adult
dogs.11
The original guidelines for VHS were
designed to be applicable across breeds
and conformations, and most dog breeds
Author Insight
Typically, a value of <8
for cats is used for
convenience (normal,
6.7-8.1). A value >8
indicates cardiomegaly,
which may indicate
underlying pathology.
h In cats, normal VHS
does not rule out heart
disease or dysfunction,
as diseases that
produce concentric
hypertrophy (eg,
hypertrophic
cardiomyopathy) will
not necessarily be
accompanied by an
enlarged cardiac
silhouette.
h
TABLE 1
NORMAL VALUES FOR SELECT DOG BREEDS
Breed
VHS Normal Range
Accepted normal VHS range
9.2-10.511 (dogs), 6.7-8.1 (cats)
Boxer
10.8-12.413
Bulldog (English and French)
11.0-14.412
Boston terrier
10.3-13.112
Cavalier King Charles spaniel
10.1-11.113
Labrador retriever
10.2-11.413
Pug
9.8-11.612
Pomeranian
9.6-11.412
Whippet
10.5-11.81
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NONCARDIAC FACTORS THAT CAN AFFECT VHS
h Interobserver variability is a known factor affecting consistent
measurement of a VHS. One study showed an average difference between
individuals of around 1 vertebrae when evaluating the same films.16 Ideally,
the same veterinarian should calculate the VHS at all time points for an
individual patient when tracking changes.
h Abnormal vertebrae, such as hemi-vertebrae, are common in breeds such
as Boston terriers and bulldogs. When present, these will impact the VHS.
The study establishing the normal values for these breeds cited this as one of
the reasons for their higher values.12
h Pericardial effusion has been shown to cause an increased VHS result. In
1 study, the majority of dogs with pericardial effusion had a VHS >12.0.17 This
should be a consideration for any dog with a generalized cardiomegaly on
thoracic radiography. A thorough physical examination and history can help
to rule this condition in or out as a cause for exercise intolerance, lethargy,
collapse, ascites, or other similar signs.
h Prolonged moderate-to-severe anemia in cats and dogs has been shown to
cause compensatory left-sided cardiomegaly and an increase in the VHS
measurement.18,19 In these patients, cardiomegaly is thought to occur
secondary to volume overload via activation of the renin-angiotensin system,
as well as through other neuroendocrine mediators.20 Initially, left atrial
enlargement develops, which is followed by left ventricular hypertrophy. Cats
can eventually develop CHF.18,19
h Right vs left lateral recumbency may impact the VHS. Several studies have
shown no difference between measurements, while others have shown that
dogs in right lateral recumbency have higher VHS values (by approximately
0.3 vertebrae).1,4,21,22 This suggests that serial measurements of the same
patient should be performed with consistent positioning; however, this may
not be clinically significant.
2A
2B
d Progressive cardiomegaly noted on annual evaluations in a dog with MVD.
52 cliniciansbrief.com April 2016
STEP-BY-STEP
CALCULATING VHS
STEP 1
Using the calipers, measure the
long axis of the heart from the
carina to the apex of the heart at its
most ventral point.
STEP 2
tarting at the cranial aspect of the
S
fourth thoracic vertebrae (T4),
transfer this measurement (ie,
heart length) to extend caudally
along the thoracic vertebrae at midbody position (Figure 1, page 49).
Add the number of vertebrae this
measurement traverses. Round to
the nearest tenth of a whole number. This is measurement “L.”
STEP 3
easure the heart at its widest
M
point (ie, the short axis) perpendicular to the line drawn for long
axis.
2C
B
STEP 4
Starting at the same point on T4, transfer this measurement to extend caudally
along the thoracic vertebrae at mid-body
position and add the number of vertebrae it traverses. Round to the nearest
tenth of a whole number. This is measurement “S.”
STEP 5
To calculate the vertebral heart scale,
add the “L” and “S” measurements
together.
References
1. Nakayama H, Nakayama T, Hamlin RL. Correlation of
cardiac enlargement as assessed by vertebral heart
size and echocardiographic and electrocardiographic
findings in dogs with evolving cardiomegaly due to
rapid ventricular pacing. JVIM. 2001;15(3):217-221.
2. Summerfield NJ, Boswood A, O’Grady MR,
et al. Efficacy of pimobendan in the prevention
of congestive heart failure or sudden death in
Doberman pinschers with preclinical dilated
cardiomyopathy (the PROTECT Study). JVIM.
2012;26(6):1337-1349.
3. O’Grady MR, O’Sullivan ML, Minors SL, Horne R.
Efficacy of benazepril hydrochloride to delay the
progression of occult dilated cardiomyopathy in
Doberman pinschers. JVIM. 2009;23(5):977-983.
4. Kvart C, Häggström J, Pedersen HD, et al. Efficacy
of enalapril for prevention of congestive heart
failure in dogs with myxomatous valve disease
and asymptomatic mitral regurgitation. JVIM.
2002;16(1):80-88.
5. Pouchelon JL, Jamet N, Gouni V, et al. Effect of
benazepril on survival and cardiac events in dogs with
asymptomatic mitral valve disease: A retrospective
study of 141 cases. JVIM. 2008;22(4):905-914.
6. Atkins C, Bonagura J, Ettinger S, et al. Guidelines
for the diagnosis and treatment of canine chronic
valvular heart disease. JVIM. 2009;23(6):1142-1150.
7. Lord P, Hansson K, Kvart C, et al. Rate of change
of heart size before congestive heart failure in
dogs with mitral regurgitation. J Small Anim Pract.
2010;51(4):210-218.
8. Lord PF, Hansson K, Carnabuci C, Kvart C, Häggström
J. Radiographic heart size and its rate of increase as
tests for onset of congestive heart failure in Cavalier
King Charles spaniels with mitral valve regurgitation.
JVIM. 2011;25(6):1312-1319.
9. Guglielmini C, Diana A, Pietra M, Di Tommaso M,
Cipone M. Use of the vertebral heart score in coughing
dogs with chronic degenerative mitral valve disease.
J Vet Med Sci. 2009;71(1):9-13.
10. Sleeper MM, Roland R, Drobatz KJ. Use of the
vertebral heart scale for differentiation of cardiac and
noncardiac causes of respiratory distress in cats: 67
cases (2002-2003). JAVMA. 2013;242(3):366-371.
11. Buchanan JW, Bücheler J. Vertebral scale system to
Other Considerations
It is important to note that a normal heart
size on thoracic radiography does not rule
out cardiac disease or dysfunction. The
VHS is a valuable tool to assess cardiac
status and should be used in conjunction
with other diagnostics (ie, physical examination, history, resting respiratory rate,
ECG, NT-proBNP, echocardiography) to
determine if treatment for cardiac disease
is warranted or if further testing is
needed based on clinical suspicion of cardiac involvement in disease. n
measure canine heart size in radiographs. JAVMA.
1995;206(2):194-199.
12. Jepsen-Grant K, Pollard RE, Johnson LR. Vertebral
heart scores in eight dog breeds. Vet Radiol
Ultrasound. 2013;54(1):3-8.
13. Lamb CR, Wikeley H, Boswood A, Pfeiffer DU. Use of
breed-specific ranges for the vertebral heart scale
as an aid to the radiographic diagnosis of cardiac
disease in dogs. Vet Rec. 2001;148(23):707-711.
14. Bavegems V, Van Caelenberg A, Duchateau L, Sys
SU, Van Bree H, De Rick A. Vertebral heart size
ranges specific for whippets. Vet Radiol Ultrasound.
2005;46(5):400-403.
15. Litster AL, Buchanan JW. Vertebral scale system to
measure heart size in radiographs of cats. JAVMA.
2000;216(2):210-214.
16. Hansson K, Häggström J, Kvart C, Lord P.
Interobserver variability of vertebral heart size
measurements in dogs with normal and enlarged
hearts. Vet Radiol Ultrasound. 2005;46(2):122-130.
17. Guglielmini C, Diana A, Santarelli G, et al. Accuracy
of radiographic vertebral heart score and sphericity
index in the detection of pericardial effusion in dogs.
JAVMA. 2012;241(8):1048-1055.
18. Wilson HE, Jasani S, Wagner TB, et al. Signs of left
heart volume overload in severely anaemic cats.
J Feline Med Surg. 2010;12(12):904-909.
19. Levine HJ, Wolk MJ, Keefe JF, Bing OH, Snow JA,
Messer JV. Myocardial mechanics and energetics in
experimental iron-deficiency anemia. Am J Physiol.
1977;232(5):H470-H477.
20. Anand IS, Chandrashekhar Y, Ferrari R, Poole-Wilson
PA, Harris PC. Pathogenesis of oedema in chronic
anaemia: Studies of body water and sodium, renal
function, haemodynamics and plasma hormones.
Br Heart J. 1993;70(4):357-362.
21. Greco A, Meomartino L, Raiano V, Fatone G, Brunetti
A. Effect of left versus right recumbency on the
vertebral heart score in normal dogs. Vet Radiol
Ultrasound. 2008;49(5):454-455.
22. Gordon SG, Saunders AB, Hariu CD, Boggess MM, Miller
MW. Retrospective review of carvedilol administration
in 38 dogs with preclinical chronic valvular heart
disease. J Vet Cardiol. 2012;14(1):243-252.
CHF = congestive heart failure
MVD = mitral valve disease
VHS = vertebral heart scale
April 2016 cliniciansbrief.com 53